KENNEDY SPACE CENTER, FLA. - Inside the wheel well behind Atlantis? right-hand main landing gear shown here, a replacement retract link is being installed. A small crack was found recently on the retract link assembly. To lower the main landing gear, a mechanical linkage released by each gear actuates the doors to the open position. The landing gear reach the full-down and extended position with 10 seconds and are locked in the down position by spring-loaded downlock bungees Atlantis is scheduled to launch in September 2005 on the second Return to Flight mission, STS-121.